NCERT Solutions for Class 11 Science Biology Chapter 6

Question 1:

A transverse section of stem is stained first with safranin and then with fast green following the usual schedule of double staining for the preparation of a permanent slide. What would be the colour of the stained xylem and phloem?
a. Red and green
b. Green and red
c. Orange and yellow
d. Purple and orange

Answer:

Safranin stains the xylem as red and fast green stains the phloem as green. However, other colours are not given by safranin and fast green.

Hence, the correct answer is option a.

Question 2:

Match the followings and choose the correct option from below

Column I		Column II
A.	Meristem	i.	Photosynthesis, storage
B.	Parenchyma	ii.	mechanical support
C.	Collenchyma	iii.	Actively dividing cells
D.	Sclerenchyma	iv.	stomata
E.	Epidermal tissue	v.	sclereids

Options:

a.	A-i,	B-iii,	C-v,	D-ii,	E-iv
b.	A-iii,	B-i,	C-ii,	D-v,	E-iv
c.	A-ii,	B-iv,	C-v,	D-i,	E-iii
d.	A-v,	B-iv,	C-iii,	D-ii,	E-i

Answer:

A meristem is a group of actively dividing cells that are involved in the growth of plants. Parenchyma is a permanent tissue that is involved in the photosynthesis and storage of food. Collenchyma is a tissue that has thick corners and provides mechanical support to the stem of the plant. Sclerenchyma is a dead tissue that has thickened sidewalls. Sclereids and fibers are of this type. The epidermis is the outer layer of the plant body and consists of stomata, epidermal appendages, hair, etc.

Hence the correct answer is option b.

Question 3:

Match the following and choose the correct option from below

Column I		Column II
A.	Cuticle	i.	guard cells
B.	Bulli form cells	ii.	single layer
C.	Stomata	iii.	waxy layer
D.	Epidermis	iv.	empty colourless cell

Options:

a.	A-iii,	B-iv,	C-i,	D-ii
b.	A-i,	B-ii,	C-iii,	D-iv
c.	A-iii,	B-ii,	C-iv,	D-i
d.	A-iii,	B-ii,	C-i,	D-iv

Answer:

Cuticle is the waxy layer present on the plant body except roots. Bulliform cells are colourless cells which are empty. When they absorb water and be comes turgid, the leaf surface is exposed.
Stomata is small pores present on the epidermis. The aperture of stomata is guarded by two kidney shaped cells called guard cells that control its opening and closing. Epidermis is a layer of single cells.

Hence the correct answer is option A.

Question 4:

Identify the simple tissue system from the following
a. Parenchyma
b. Xylem
c. Epidermis
d. Phloem

Answer:

Xylem and phloem are the complex tissue found in all vascular plants. Parenchyma is a tissue present in all organs of the plant such as roots, stems, leaves etc. While, epidermis is single layered structure that is present on the entire body surface. This makes it a simple tissue system.

Hence the correct answer is option C.

Question 5:

Cells of this tissue are living and show angular wall thickening. They also provide mechanical support. The tissue is
a. Xylem
b. Sclerenchyma
c. Collenchyma
d. Epidermis

Answer:

Collenchyma is a simple tissue that provides mechanical strength to the plant. The cells are thickened at the corners. Xylem is a complex conductive tissue that transports water. Sclerenchyma is a dead tissue that is present in hard areas of the plant. Epidermis is a single layer tissue on the surface of the plant.

Hence the correct answer is option C.

Question 6:

Epiblema of roots is equivalent to
a. Pericycle
b. Endodermis
c. Epidermis
d. Stele

Answer:

Instead of the epidermis, in roots, the single-layered structure is called epiblema.

Hence, the correct answer is option c.

Question 7:

A conjoint and open vascular bundle will be observed in the transverse section of
a. Monocot root
b. Monocot stem
c. Dicot root
d. Dicot stem

Answer:

In the dicot stem, conjoint and open vascular bundles are observed. Vascular bundles are said to be open when cambium is present in between the xylem and phloem. Conjoint means xylem and phloem are united and are present on the same radius.

Hence the correct answer is option d.

Question 8:

Interfascicular cambium and cork cambium are formed due to
a. Cell division
b. Cell differentiation
c. Cell dedifferentiation
d. Redifferentiation

Answer:

Interfascicular cambium and cork cambium are formed due to cell de-differentiation. De-differentiation is a phenomenon of differentiated cell regaining its capacity for cell division under certain conditions.
Interfascicular cambium and cork cambium are formed from fully differentiated parenchyma cells.

Hence the correct answer is option B.

Question 9:

Phellogen and Phellem respectively denote
a. Cork and cork cambium
b. Cork cambium and cork
c. Secondary cortex and cork
d. Cork and secondary cortex

Answer:

Cortical cells get differentiated to give rise to meristematic tissue called cork cambium or phellogen. Phellogen, on the outer side, differentiates into cork or phellem, and in the inner region, it forms phelloderm.

Hence the correct answer is option b.

Question 10:

In which of the following pairs of parts of a flowering plant is epidermis absent?
a. Root tip and shoot tip
b. Shoot bud and floral bud
c. Ovule and seed
d. Petiole and pedicel

Answer:

The epidermis is absent in the root tip and shoots tip of a plant. These parts have high meristematic activity as the cells in this region are actively dividing. So the cells do not get differentiated to epidermal tissue.

Hence, the correct answer is option a.

Question 11:

How many shoot apical meristems are likely to be present in a twig of a plant possessing 4 branches and 26 leaves
a. 26
b. 1
c. 5
d. 30
e. 4

Answer:

Plants having 4 branches and 26 leaves will have 5 growing apices (i.e., 4 apical meristems at the tip of four branches and one growing apex of the main shoot apex.

Hence the correct answer is option C.

Question 12:

A piece of wood having no vessels (trachea) must belong to
a. Teak
b. Mango
c. Pine
d. Palm

Answer:

Pine is a gymnosperm and plants belonging to this group do not have vessels, instead they have tracheids. Other plants given in the option are angiosperms that contain vessels, tracheids, parenchyma and fibres.

Hence the correct answer is option C.

Question 13:

A plant tissue, when stained, showed the presence of hemicellulose and pectin in cell wall of its cells. The tissue represents
a. Collenchyma
b. Sclerenchyma
c. Xylem
d. Meristem

Answer:

Deposition of pectin and hemicellulose makes the corners of the collenchyma cells thicker. These groups of cells are meant for mechanical support.

Hence the correct answer is option a.

Question 14:

In conifers fibres are likely to be absent in
a. Secondary phloem
b. Secondary xylem
c. Primary phloem
d. Leaves

Answer:

Fibers are absent in the secondary xylem. This is usually seen in conifers. Elongated cells of sclerenchyma are called fibers.

Hence the correct answer is option b.

Question 15:

When we peel the skin of a potato tuber, we remove
a. Periderm
b. Epidermis
c. Cuticle
d. Sapwood

Answer:

The outer epidermal layer of the stem is known as the periderm. However, the potato is an underground stem, thus we are actually removing the periderm.

Hence, the correct answer is option a.

Question 16:

A vessel less piece of stem possessing prominent sieve tubes would belong to
a. Pinus
b. Eucalyptus
c. Grass
d. Trochodendron

Answer:

Trochodendron is a genus that has a unique feature of the angiosperms, i.e., it lacks the vessel elements in its wood, but has prominent sieve tube cells.

Hence, the correct answer is option d.

Question 17:

Which one of the following cell types always divides by anticlinal cell division?
a. fusiform initial cells
b, root cap
c. protoderm
d. phellogen

Answer:

Protoderm cells always divide by anticlinal cell division to form a uniseriate epidermis.

Hence, the correct answer is option c.

Question 18:

What is the fate of primary xylem in a dicot root showing extensive secondary growth?
a. It is retained in the centre of the axis
b. It gets crushed
c. May or may not get crushed
d. It gets surrounded by primary phloem

Answer:

During the secondary growth of the dicot root, the primary xylem is retained in the center of the axis but the phloem is pushed
outside and crushed.

Hence, the correct answer is option a.

Question 1:

Product of photosynthesis is transported from the leaves to various parts of the plants and stored in some cell before being utilised. What are the cells/ tissues that store them?

Answer:

Parenchymatous cells present in roots or stems store the food that is prepared through photosynthesis. The food gets stored in the form of starch.

Question 2:

Protoxylem is the first formed xylem. If the protoxylem lies next to phloem what kind of arrangement of xylem would you call it?

Answer:

If the protoxylem lies next to phloem then the arrangement is called an exarch which is found in roots.

Question 3:

What is the function of phloem parenchyma?

Answer:

The main function of the phloem parenchyma is to store and transport food. Other substances like resins, latex etc. are also stored by these tissues.

Question 4:

What is present on the surface of the leaves which helps the plant prevent loss of water but is absent in roots?

Answer:

The cuticle is a waxy layer which is present on the leaves or the entire body surface but is absent in roots. It prevents the loss of water through the plant surface.

Question 5:

What is the epidermal cell modification in plants which prevents water loss?

Answer:

Epidermal cell modification in plants which prevent water loss are the bulliform cells. These cells are present in monocots or grasses. They help in shutting down stomata during stress conditions and thus reduce water loss.

Question 6:

What part of the plant would show the following:
a. Radial vascular bundle
b. Polyarch xylem
c. Well developed pith

Answer:

(a) Radial vascular bundles are present in roots.
(b) Polyarch xylem is present in monocot roots.
(c) Well-developed pith is found in the dicot stem and monocot roots which are formed of parenchymatous cells with intercellular spaces.

Question 7:

What are the cells that make the leaves curl in plants during water stress?

Answer:

Bulliform cells are bubble shaped cells that are present in grasses and make the leaves cure during water stress as there is turgor pressure in the leaves that reduce transpiration.

Question 8:

What constitutes the cambial ring?

Answer:

The cambial ring is a ring which is made up of interfascicular and intrafascicular cambia. It is formed due to the meristematic activity of cambium.

Question 9:

Give one basic functional difference between phellogen and phelloderm.

Answer:

Phelloderm is a permanent tissue while phellogen is a meristematic tissue. Cork cambium or phellogen develops from the cortical cells. These cells divide actively and forms phellem on outside and phelloderm on the innerside.

Question 10:

Arrange the following in the sequence you would find them in a plant starting from the periphery – phellem, phellogen, phelloderm.

Answer:

\underset{(Outermost layer)}{Phellem} \to \underset{(Cork Cambium)}{Phellogen} \to \underset{(Secondary Cortex)}{Phelloderm}

Question 11:

If one debarks a tree, what parts of the plant is being removed?

Answer:

Debark a tree means removal of bark from the tree. Bark consists of tissues like cork, cork cambium, secondary cortex and secondary phloem. Thus, debarking will remove these tissues.

Question 12:

The cross-section of a plant material showed the following features when viewed under the microscope.
a. The vascular bundles were radially arranged.
b. Four xylem strands with exarch condition of protoxylem.
To which organ should it be assigned?

Answer:

The cross-section of dicot root will show these features given in the question. Vascular bundles are present on the separate radii and are arranged alternately, thus called radial arrangement.

Question 13:

What do hard wood and soft wood stand for?

Answer:

Softwood is a gymnospermic wood and hardwood is an angiospermic wood. Softwood contains tracheids white hardwood contains tracheids and vessels.

Question 1:

While eating peach or pear it is usually seen that some stone like structures get entangled in the teeth, what are these stone like structures called?

Answer:

The stone like structures which are present in the pulpy part of the fruit such as peach and pear are called sclereids. These are the selerenchymatous tissues which are dead in nature and provide mechanical support to the soft tissue.

Question 2:

What is the commercial source of cork? How is it formed in the plant?

Answer:

The commercial source of cork is the cork tissue of Quercus suber. Cork is formed by cork cambium or phellogen cells. Cork cambium cells divide periclinal, by cutting cells towards the inside and outside. The cells are cut off the outside become suberised and dead. These are compactly packed in radial rows and don't have intercellular spaces, and form cork of phellem. Cork is impervious to water as it is suberised and provides protection to the underlined tissue.

Question 3:

Below is a list of plant fibres. From which part of the plant these are obtained
a. Coir
b. Hemp
c. Cotton
d. Jute

Answer:

(a) Coir is the natural fibre obtained from the husk of a coconut. It is the fibrous mesoderm of coconut.
(b) Hemp is a fibre obtained from the stems of Cannabis sativa. It is the best fibre obtained from secondary phloem.
(c) Cotton is fibre which is the epidermal growth of cotton seeds. It is made up of cellulose.
(d) Jute is a natural fibre that is obtained from the storm of Corchorus capsularis and is made up of cellulose and lignin.

Question 4:

What are the characteristic differences found in the vascular tissue of gymnosperms and angiosperms?

Answer:

Vascular tissue of Gymnosperm	Vascular tissue of Angiosperm
Xylem in gymnosperms lacks vessels instead they have tracheids.	Xylem in angiosperms have vessels instead they lack tracheids.
Phloem lacks companion cells and have albuminous cells.	Phloem has companion cells and lack albuminous cells.

Question 5:

Epidermal cells are often modified to perform specialized functions in plants. Name some of them and the function they perform.

Answer:

Epidermal cells have the following modifications

(1) Root hair:

Unicellular hairs are the extensions of epiblema cells of roots. They increase the absorptive surface area for water and minerals to be absorbed from the soil.

(2) Trichomes /Stem hairs:

These are epidermal cell modifications that may be unicellular or multicellular. They help in preventing water loss during transpiration.

(3) Bulliform cells:

These cells are present in grasses that help in closure of stomata under unfavourable or stress conditions, thus helps to prevent water loss.

Question 6:

The lawn grass (Cynodon dactylon) needs to be mowed frequently to prevent its overgrowth. Which tissue is responsible for its rapid growth?

Answer:

The meristematic tissue is responsible for rapid growth of lawn grass. When the apex of lawn grass is cut frequently, the apical meristem is destroyed and prevents its growth in height. This also promotes growth of lateral branches that makes it more bushy.

Question 7:

Plants require water for their survival. But when watered excessively, plants die. Discuss.

Answer:

When plants are watered in excess, the air gets trapped between the soil particles. This drops the oxygen concentration in the roots and the respiration of roots gets hampered. As when roots die, water and mineral absorption is stopped which leads to death of the plant.

Question 8:

A transverse section of the trunk of a tree shows concentric rings which are known as growth rings. How are these rings formed? What is the significance of these rings?

Answer:

The concentric, rings are also called annual rings that are formed due to the secondary growth in the trunk. Secondary growth occurs in dicot trees due to the activity of cambium. This cambium activity is more in spring season than in winter this wood formed in spring has larger xylem as compared to wood formed in winter. This results in formation of two rings called growth rings. Light coloured wood is formed in spring while dark coloured wood is formed in winters. This gives the appearance of concentric rings that also helps in determining the age of trees.

Question 9:

Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.

Answer:

The trunk of some of the aged tree species appears to be composed of several fused trunks due to anatomical abnormality. It is an abnormal type of secondary growth where a regular vascular cambium or cork cambium is not formed in its normal position. The accessory or additional vascular bundles give the false appearance of fusion of multiple trunks with each other.

Question 10:

What is the difference between lenticels and stomata?

Answer:

Some of the following differences between lenticels and stomata are following:


Lenticels	Stomata

Question 11:

Write the function of
a. Sieve tube
b. Interfasicular cambium
c. Collenchyma
d. Aerenchyma

Answer:

a) Sieve tubes are the main vessels involved in the translocation of prepared food within the angiosperm plant body.

b) Interfascicular cambium along with intrafascicular cambium combines to form the secondary cambium growth ring, which is responsible for lateral, secondary growth of vascular tissue.

c) Collenchyma is the type of simple permanent tissue. It is made of living cells with irregularly thickened cell walls. Cells of collenchymatous tissue are polygonal in shape and have no intercellular space between them. Collenchymatous tissue is primarily meant to provide strength along with the agility to bend.

d) Aerenchymatous cells are modified type of parenchymatous cells (simple permanent tissue). It is a spongy tissue in shoots and roots of some plants providing passage for exchange of gases between various plant parts. In case of many aquatic plants they are generally responsible for providing buoyancy to the plant parts due the presence of air spaces between their cells.

Question 12:

The stomatal pore is guarded by two kidney shaped guard cells. Name the epidermal cells surrounding the guard cells. How does a guard cell differ from an epidermal cell? Use a diagram to illustrate your answer.

Answer:

The modified epidermal cells around the guard cells are termed subsidiary cells.

Differences between a guard cell and an epidermal cell are as follows:

Epidermal Cell	Guard Cell
(i) They are flat, barrel-shaped.	(i) They are shaped like kidney beans.
(ii) Chloroplast is often absent.	(ii) Chloroplast present.
(iii) Smaller in size in comparison to the guard cell.	(iii) Larger in size in comparison to the epidermal cell.
(iv) Cell Wall is uniform.	(iv) Cell Wall is not uniform.

Question 13:

Point out the differences in the anatomy of, leaf of peepal (Ficus religiosa) and maize (Zea mays). Draw the diagrams and label the differences.

Answer:

Peepal or Ficus religiosa is a dicot plant where else maize or Zea mays is a monocot plant. Thus following anatomical differences are observed between the leaves of peepal and maize:

Peepal Leaf	Maize Leaf
(i) Leaves are dorsiventral	(i) Leaves are isobilateral
(ii) Leaves have stomata only on the lower surface	(ii) Leaves have stomata on both the surfaces.
(iii) Mesophyll cells present are of two types: pallisade and spongy.	(iii) Mesophyll cells present are of one kind only.
(iv)Parenchymatous and collenchymatous cells are found around vascular bundles.	(iv) Sclerenchymatous cells are found around vascular bundles.
(v) Bulliform cells are absent in the leaf	(v) Bulliform cells are present in the leaf.

Question 14:

Palm is a monocotyledonous plant, yet it increases in girth. Why and how?

Answer:

Palm is a monot plant that shows secondary growth i.e., increase in girth. It is the phenomenon in which parenchymatous cells of the ground tissue enlarge and divide. Thus, repeated division causes increase in the girth of the stem. This type of growth is termed as diffused secondary growth.

Question 1:

The arrangement of ovules within the ovary is known as placentation. What does the term placenta refer to? Draw various types of placentations in the flower as seen in T.S. and V.S.

Answer:

Placentation is the arrangement of ovules within the ovary. The placenta is soft cushion-like, flattened tissue with which the ovules are attached to the inner walls of the ovary.

The Placentations are of different types :

(1) Axile Placentation :

Ovules are attached to the central axis and the marginal of the placenta grow inward and fuse, it forms a multilocular ovary.
Example - China rose, tomato, etc.

(2) Marginal Placentation :

The placenta forms a ridge along the ventral suture of the ovary and ovules are borne on this ridge forming two rows.
Example - Pea.

(3) Parietal Placentation :

Ovaries develop on the inner wall of the ovaryon the periphery. Ovary is one chambered but becomes two chambered due to formation of false septum.
Example- Mustard.

(4) Free Central Placentation :

Ovaries are present on the central axis of ovary and septum is absent, the ovary becomes unilocular. Example- Dianthus and Primose.

(5) Basal Placentation :

Placenta develops at the base of the ovary and a single ovule is attached to it.
Example- sunflower.

Question 2:

Deciduous plants shed their leaves during summer or in autumn. This process of shedding of leaves is called abscission. Apart from physiological changes what anatomical mechanism is involved in the abscission of leaves.

Answer:

Abscission is a phenomenon of shedding of leaves during harsh seasons. It occurs as a result of many physio-chemical changes in the plant. Some of the main anatomical changes involved in the process of abscission of leaves are following:

Prior to abscission of leaf an abscission zone is created at the base of a leaf. This abscission zone consist of top and bottom layers. The cells of the top layer possess weak cell walls and those of the bottom layer have strong cell walls. During winters or at the time of abscission, the cells of the bottom layers expand, leading to the rupturing of the cell walls of the cells at the top layer. This rupturing of the cells of the top layer leads to breakage of the leaf at the base of its petiole from the branch, leading to abscission. Another reason of leaf abscission can also be the loss of chlorophyll in leaves.

Question 3:

Is Pinus an evergreen tree? Comment.

Answer:

Pinus is an evergreen plant as its leaves are never shed in all four seasons. Pinus loses and sheds its leaves at regular intervals throughout the year and never at one particular season. Angiosperms, flowering plants under conditions of extreme cold shed their leaves and become dormant, thus the case is not with Pinus as it's a gymnosperm.

The leaves in gymnosperm are well adapted to extreme conditions. For example Pinus have needle-like leaves having sunken stomata, which reduces the transpiration. Hence, in scanty rainfall, low precipitation, or decreased root absorption areas, habitats with low temperature, Pinus grows and manufacture food during this condition. This shows that Pinus is an evergreen tree.

Question 4:

Assume that a pencil box held in your hand, represents a plant cell. In how many possible planes can it be cut? Indicate these cuts with the help of line drawings.

Answer:

A plant cell can be cut in following planes:
(I) If it cuts in different plane through central axis of the plant, it will result in radial symmetry.

(II) If it cuts into two equal halves, it will result in bilateral symmetry.

Question 5:

Each of the following terms has some anatomical significance. What do these terms mean? Explain with the help of line diagrams.
a. Plasmodesmata
b. Middle lamella
c. Secondary wall

Answer:

Structure	Function
Plasmodesmata are the microscopic channels between two cells through the cell wall.	It allows transportation of substances between the plant cells through symplastic pathway.
Middle Lamella is a layer in the cell wall which is mainly made up of calcium pectate.	It helps in cementing the two adjacent cells.
Secondary Wall is a non-extensible layer made up of hemicellulose in the cell wall of plant cells.	It provides rigidity to the cell wall of the plant cell.

Question 6:

Distinguish between the following:
a. Exarch and endarch
b. Stele and vascular bundle
c. Protoxylem and metaxylem
d. Interfasicular cambium and intrafasicular cambium
e. Open and closed vascular bundles
f. Stem hair and root hair

Answer:

a) Exarch	Endarch
(i) Condition in which protoxylem is present towards the periphery and metaxylem is present towards the centre. (ii) It is found in roots.	(i) Condition in which protoxylem is present towards the centre and metaxylem is present towards the periphery. (ii) It is foud in stem.
b) Stele	Vascular bundle
(i) It is the central part of root or stem. Consists of vascular tissue, ground tissue, pith.	(i) Vascular bundle consist of xylem and phloem and is a part of stele.
c) Protoxylem	Metaxylem
(i) Earlier formed xylem is protoxylem which matures before the growth and differentiation of plant organs.	(i) Later formed xylem is metaxylem which matures after the growth and differentiation of plant organs.
d) Intrafascicular Cambium	Interfascicular Cambium
(i) It is present in between the primary xylem and primary phloem as in dicot stems.	(i) It is present in between the two vascular bundles making the cambium continuous and forming a complete ring of cambium.
e)Open vascular bundle	Closed vascular bundle
(i) Cambium is present in between xylem and phloem tissue and are capable of secondary growth. (ii) Found in dicots	(i) Cambium is present in between xylem and phloem tissue and are not capable of secondary growth. (ii) Found in monocots.
f) Stem hair	Root hair
(i) Stem hair are epidermal outgrowths and are multicellular known as trichomes. (ii) They prevent water loss.	(i) Root hair are also epidermal outgrowths and are unicellular. (ii) They increase absorptive surface area for water and minerals.

NCERT Solutions for Class 11 Science Biology Chapter 6 - Anatomy Of Flowering Plants

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